1. Field of the Invention
This invention relates to a magnetic storage device and, more particularly, a magnetic storage device comprising memory cells including magneto-resistive elements.
2. Description of the Related Art
Recently, a magnetic storage device (magnetic random access memory: MRAM) including magneto-resistive elements using the TMR (Tunneling Magneto-Resistive) effect has been noticed (see, for example, ISSCC2000 Technical Digest p.128, “A 10 ns Read and Write Non-Volatile Memory Array Using a Magnetic Tunnel Junction and FET Switch in each Cell”).
The MRAM comprises a plurality of alloys and needs to be formed basically in a low temperature process. The high-speed processing and nonvolatility of the MRAM are expected to show the maximum performance by use with a high-speed logic LSI.
In the high-speed logic LSI, a low dielectric constant film (hereinafter Low-k film) remarkably tends to be used as an interlayer insulation film. The Low-k film is higher in moisture absorbency than a pure silicon oxide (SiO2) film, since it has a porous structure including metal impurities or similar reasons. It is therefore difficult to assure enough adhesion on an interface between the Low-k film serving as the interlayer insulation film and a metal thin film used for the MRAM.
Moreover, in a case of the MRAM, if writing on a free layer is repeated, stress resulting from magnetostriction may easily induce exfoliation in the interface and cause problems on reliability.